Improve lint message for match-same-arms lint

[rust.git] / clippy_lints / src / matches.rs

diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs
index 50e2898bdaae7a315a4b2d729f2f652b71763430..386349d9f593f64e4825489eb52d2766b57c02fe 100644 (file)
--- a/clippy_lints/src/matches.rs
+++ b/clippy_lints/src/matches.rs
@@ -1,4 +1,4 @@
-use crate::consts::{constant, miri_to_const, Constant};
+use clippy_utils::consts::{constant, miri_to_const, Constant};
 use clippy_utils::diagnostics::{
     multispan_sugg, span_lint_and_help, span_lint_and_note, span_lint_and_sugg, span_lint_and_then,
 };
@@ -1144,7 +1144,7 @@ fn check_wild_enum_match(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>])
                 "try this",
                 suggestions.join(" | "),
                 Applicability::MaybeIncorrect,
-            )
+            );
         },
     };
 }
@@ -1242,7 +1242,7 @@ fn check_match_as_ref(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], exp
                     cast,
                 ),
                 applicability,
-            )
+            );
         }
     }
 }
@@ -1478,15 +1478,34 @@ fn check_match_single_binding<'a>(cx: &LateContext<'a>, ex: &Expr<'a>, arms: &[A
             );
         },
         PatKind::Wild => {
-            span_lint_and_sugg(
-                cx,
-                MATCH_SINGLE_BINDING,
-                expr.span,
-                "this match could be replaced by its body itself",
-                "consider using the match body instead",
-                snippet_body,
-                Applicability::MachineApplicable,
-            );
+            if ex.can_have_side_effects() {
+                let indent = " ".repeat(indent_of(cx, expr.span).unwrap_or(0));
+                let sugg = format!(
+                    "{};\n{}{}",
+                    snippet_with_applicability(cx, ex.span, "..", &mut applicability),
+                    indent,
+                    snippet_body
+                );
+                span_lint_and_sugg(
+                    cx,
+                    MATCH_SINGLE_BINDING,
+                    expr.span,
+                    "this match could be replaced by its scrutinee and body",
+                    "consider using the scrutinee and body instead",
+                    sugg,
+                    applicability,
+                );
+            } else {
+                span_lint_and_sugg(
+                    cx,
+                    MATCH_SINGLE_BINDING,
+                    expr.span,
+                    "this match could be replaced by its body itself",
+                    "consider using the match body instead",
+                    snippet_body,
+                    Applicability::MachineApplicable,
+                );
+            }
         },
         _ => (),
     }
@@ -1590,9 +1609,9 @@ fn is_none_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> bool {
 // Checks if arm has the form `Some(ref v) => Some(v)` (checks for `ref` and `ref mut`)
 fn is_ref_some_arm(cx: &LateContext<'_>, arm: &Arm<'_>) -> Option<BindingAnnotation> {
     if_chain! {
-        if let PatKind::TupleStruct(ref qpath, pats, _) = arm.pat.kind;
+        if let PatKind::TupleStruct(ref qpath, [first_pat, ..], _) = arm.pat.kind;
         if is_lang_ctor(cx, qpath, OptionSome);
-        if let PatKind::Binding(rb, .., ident, _) = pats[0].kind;
+        if let PatKind::Binding(rb, .., ident, _) = first_pat.kind;
         if rb == BindingAnnotation::Ref || rb == BindingAnnotation::RefMut;
         if let ExprKind::Call(e, args) = remove_blocks(arm.body).kind;
         if let ExprKind::Path(ref some_path) = e.kind;
@@ -1728,7 +1747,7 @@ pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
             match match_source {
                 MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
                 MatchSource::IfLetDesugar { contains_else_clause } => {
-                    find_sugg_for_if_let(cx, expr, op, &arms[0], "if", *contains_else_clause)
+                    find_sugg_for_if_let(cx, expr, op, &arms[0], "if", *contains_else_clause);
                 },
                 MatchSource::WhileLetDesugar => find_sugg_for_if_let(cx, expr, op, &arms[0], "while", false),
                 _ => {},
@@ -1857,7 +1876,7 @@ fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
                             {
                                 self.res = true;
                             } else {
-                                self.visit_expr(self_arg)
+                                self.visit_expr(self_arg);
                             }
                         }
                         args.iter().for_each(|arg| self.visit_expr(arg));
@@ -2247,7 +2266,8 @@ fn lint_match_arms<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) {
                             ),
                         );
                     } else {
-                        diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs));
+                        diag.span_help(i.pat.span, &format!("consider refactoring into `{} | {}`", lhs, rhs,))
+                            .help("...or consider changing the match arm bodies");
                     }
                 },
             );